As a first step towards developing an effective audio
analogue, let us examine communication through the printed
page. The printed page is passive: it is a two-dimensional
visual display with marks on it. The person reading the printed
page can either scan the material linearly or browse through
parts of the document. Visual layout (the way the marks appear
on paper) enables such browsing. Thus, rather than laying all
the text in a naive manner on the page, we exploit concepts
such as line and paragraph breaks to allow the reader to
perceive chunks of the printed matter and to
selectively read specific portions of the text being
presented.

The dpower of the printed medium lies in the eye's ability
to browse text laid out on a two-dimensional display. When
reading a paper, we are able to skim through the text, focusing
on paragraphs of interest, and quickly scan across to the
bottom of a page when we see a reference being made to a
footnote.